Method of defining a mask pattern for a photoresist layer in semiconductor fabrication

Abstract

A method of defining a mask pattern for a photoresist layer in semiconductor fabrication. The method coats a photoresist layer containing an additive on a dielectric layer. The photoresist layer has an opening formed therein. The additive is 2,2′-azo-bis-isobutyronitride (AIBN) or phenyl-azo-triphenylmethane. The photoresist layer is exposed and developed. Then, a hard baking step is performed. A UV curing or a hot curing step is performed on the photoresist layer. As a result, the additive in the photoresist layer reacts to form nitrogen (N 2 ) gas. Nitrogen gas makes the photoresist layer expand. The opening is decreased by the expansion of the photoresist layer. The dielectric layer is etched according to the expanded photoresist layer so that a via or a trench, which is smaller than a conventional one, is formed.

What is claimed is:  
     
       1. A method of defining a mask pattern for a photoresist layer in semiconductor fabrication, wherein a substrate comprises a dielectric layer formed thereon is provided, comprising the steps of: 
       forming a photoresist layer on the dielectric layer, wherein a compound is added to the photoresist layer;  
       exposing and developing the photoresist layer to form at least one opening within the photoresist layer; and  
       providing a UV light to irradiate the photoresist layer, wherein the UV light causes the compound to react and thereby form gas which expands the photoresist layer.  
     
     
       2. The method according to  claim 1 , wherein the compound comprises 2,2′-azo-bis-isobutyronitride (AIBN). 
     
     
       3. The method according to  claim 1 , wherein the compound comprises phenyl-azo-triphenylmethane. 
     
     
       4. The method according to  claim 1 , wherein the gas comprises nitrogen. 
     
     
       5. The method according to  claim 1 , wherein a wavelength of the UV light is not larger than 3600 Å. 
     
     
       6. A method of forming a opening within a provided dielectric layer, comprising the steps of: 
       forming a photoresist layer with an additive on the provided dielectric layer, wherein the additive reacts to release a gas while a UV light is incident thereon;  
       exposing and developing the photoresist layer to form an opening pattern within the photoresist layer;  
       exposing the photoresist layer to the UV light to release the gas and further to expand the photoresist layer;  
       etching the dielectric layer while using the expanded photoresist layer as a mask to form the opening in the dielectric layer; and  
       removing the photoresist layer.  
     
     
       7. The method according to  claim 6 , wherein the compound comprises 2,2′-azo-bis-isobutyronitride (AIBN). 
     
     
       8. The method according to  claim 6 , wherein the compound comprises phenyl-azo-triphenylmethane. 
     
     
       9. The method according to  claim 6 , wherein the gas comprises nitrogen. 
     
     
       10. The method according to  claim 6 , wherein a wavelength of the UV light is not larger than 3600 Å.